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TYPO3CMS

CVE-2021-21370

MEDIUM · 5.4 CVSS v3.1 Published 2021-03-23
Fix available
A fix is available. Upgrade to 7.6.51 / 8.7.40 or later.
See remediation →
58/100
Remediation priority · Elevated
Remotely reachable

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
TYPO3 is an open source PHP based web content management system. In TYPO3 before versions 7.6.51, 8.7.40, 9.5.25, 10.4.14, 11.1.1 it has been discovered that content elements of type _menu_ are vulnerable to cross-site scripting when their referenced items get previewed in the page module. A valid backend user account is needed to exploit this vulnerability. This is fixed in versions 7.6.51, 8.7.40, 9.5.25, 10.4.14, 11.1.1.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

TYPO3 CMS contains a stored cross-site scripting (XSS) vulnerability in the page module's menu content element preview functionality. An authenticated backend user with access to menu content elements can inject malicious scripts through crafted menu item references that execute when previewed by other backend users.

MitigationUpgrade TYPO3 to version 7.6.51, 8.7.40, 9.5.25, 10.4.14, 11.1.1 or later. Apply vendor patches if available for intermediate versions.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
TYPO3CMS
Affected:>= 7.0.0, < 7.6.51>= 8.0.0, < 8.7.40>= 9.0.0, < 9.5.25>= 10.0.0, < 10.4.14>= 11.0.0, < 11.1.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed TYPO3 version
    Check the VERSION file in the TYPO3 root directory, or look in typo3/sysext/core/composer.json for the 'version' field, or access the backend Admin Tools > About > Installation and view the installed TYPO3 version.
    Affected if The installed version falls within any of these ranges: 7.0.0 to 7.6.50, 8.0.0 to 8.7.39, 9.0.0 to 9.5.24, 10.0.0 to 10.4.13, or 11.0.0 to 11.1.0.
  2. Verify backend authentication is enabled
    Check if the TYPO3 backend is accessible by attempting to log in at /typo3/ or by examining the installation for disabled backend authentication in LocalConfiguration.php or AdditionalConfiguration.php.
    Affected if Backend authentication is active and users can log in to the TYPO3 backend.
  3. Check for presence of menu content elements
    Query the database table tt_content for records where CType = 'menu' or look in the backend under Web > Page > select a page > Content > New > Menu to see if menu content elements are available.
    Affected if Menu content elements exist on the site or are permitted in the content element configuration.
  4. Confirm page module preview is accessible to users
    Log in as a backend user and navigate to Web > Page, select a page containing menu content elements, and view the page module where the preview renders.
    Affected if The page module preview functionality is accessible to authenticated backend users.

You are affected if your TYPO3 installation version is within the affected ranges AND your backend allows authenticated users access to menu content elements and the page module preview.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to 7.6.51 / 8.7.40 / 9.5.25 or later
Fixed in 7.6.518.7.409.5.25
Interim mitigation

Upgrade TYPO3 to version 7.6.51, 8.7.40, 9.5.25, 10.4.14, 11.1.1 or later. Apply vendor patches if available for intermediate versions.

Fix this in TYPO3 Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing8.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,800
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-21370 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data